Reflecting-condenser for enlarging photographs.



R. D. GRAY. REFLECTING CONDENSER FOR ENLARGINQ PHOTOGRAPHS.

Y Patented Jan. 15, 1918.,

A TTOR/VEYS on through a 10. a single source of artificial ly-nlUlEl-KTED RUBERT It);

REFLEUTIlll'G-CQNDEIMSER To aZZ whom it may concern:

Be it known that l, lftoennr D. GRAY, citizen of the United States, anda resident of Ridgewood, in the county of 'Bergenand State of NewJersey, have invented anew and Improved ReflectingCondenser forEnlarging Photographs, of which the following is a full, clear, andexact description.

The invention relates to apparatus for enlarging photographs With theaid of artificial light, and its object is to provide a new and improvedreflecting condense for enlarging photographs with the aid of a singlesource of artificial light, and arranged to insure a uniformillumination of the image thrown on the sensitized medium held on thescreen or disk;

In apparatus of this type as heretofore constructed and used forconverging artiiicial light from a single source so that it Will passthrough all parts of a negative and projecting lens, it has been acommon fault that the portions of the negative farthest from the centerand axis of the apparatus appear less brilliantly lighted than themiddle portion owing to the greater distance traversed by the rays oflight which pass through such outer portions, and hence the image thrownon the screen is not as uniformly illuminated as it should be in orderto obtain the best results. In order to overcome this defect use is madeof a reflect ing condenser having reflecting portions of varyingintensity.

A practical embodiment ofthe invention .is represented'in theaccompanying drawings forming a part of this specification, in whichsimilar characters of reference indi cate corresponding parts in all theviews.

Figure l is a front perspective view of the mounted reflectingcondenser;

2 is a front perspective view of. the reflecting condenser; and

Fig. 3 is a diagrammatic view of the ap paratus for enlargingphotographs loy the aid of artificial light and provided With theimproved reflecting condenser.

The apparatus for enlarging photographs consists of an improvedreflecti" rcondenser ll, diffuser 12 of ground glass or other ma terialarranged in front of the refiectin con. denser 10, with the negativeifito he larged in front of the ditfuserlfl and spaced from the lens 14:for throwing the enlarged image on'the screen or disk sourceSpecification of tterial no. Ii.'.?l,7lil.

tters Eatent.

of light 11 is prefcrabl in the form of an incandescent electric lamp,extending through an opening 16 formed centrally in the reflectingcondenser 10, as plainly shown 60 in Fig. 2.

The type of invention to Which my improvement applies is a reflectorcomposed of segmental plane mirrors in two or more rows such, forinstance, as described in the Let- 65 ters Patent of the United States,No. 1,133,955, granted to me March 30, 1915, but it is expresslyunderstood that the present improvement may apply to other forms ofreflectors such as spherical, parabolic, etc, and Whether suchreflectors have segmental plane surfaces or a continuous curve. hasshown in Fig. 1, a series of concentric rows of mirrors 20, 21, 22, :lll23 are provided, mounted on a suitable support and with the mirrors inthe innermost and outermost rows 20 and 23 of a high reflecting powerand With the mirrors in each of the rows 21 and 2 arranged alternatelyof higher and lower power, and with the n'iirrors in the row 21Ststaggcred relativelv to the mirrors in the row 22, as plainlyindicated, in l and The higher power ll'llllOFS used are preferablyprovided with silvered backs, While those of lesser power may be sheetglass 85 coated on the back With aluminum bronze, white paint, lead ortin foil, or the clear glass used Without coating and the surface of thereflector case polished or painted of a desired reflecting power, withor Without clear glass segments over these parts. ll hitc or opal glassmay be used.' Elilvered mirrors may he reduced in reflecting power bythe removal of portions of the coating in lines 1' dots or ground on oneside. l l hen altera nated in a row the silvered reflectors alterhatingwith the lesser power, the Widths may be selected to produce the desiredamount of light on particular parts of the projection. The innermost rowof mirrors 20 is of high reflecting power to compensate for the blanlaropening in the center of the refl ct condenser. As shown in l ig. 1, the

from the son the rows of mirrors 2t, 21, t'user 12,

pass throng ioins the n t a or 1 e'es iven h t q w L9 Ii tor, thusproducing a nomogeneouc surface at the plane occupied by the negative13. When light-spots from the view point of the lens 14 without adiffuser appear uniformly spaced apart, then the diffuser is interposedand an' image of the whole .projected in the usual manner. Theilluminosity of parts of the screen 15 now corresponds with the natureor, reflecting power of the segmental mirrors in alinement therewith,and these having been positioned in the-reflector to compensate for thedifferences in light intensity received on their surfaces at differentdistances from the light source, it-

is evident that the entire surface of the proiected image will beuniformly lighted.- The amp house and other parts of the apparatus (notshown) and used for holding negative, screen and lens shouldprovideadjusting distance between reflector and negative in order thatthe negative and diffusing screen may be placed at a distance from thereflector at which the cone of light of the inner rows of mirrors closethe aforesaid blank opening. r

Having thus described my invention, I claim as new and desire to-secureby Letters Patent .1. As an article of manufacture, a coning andconcentric rows of plane mirrors, of which the outermost and innermostrows of mirrors have a reflecting power in excess of the intermediaterow of mirrors, the intermediate row of mirrors being formedof twoconcentric sectlons with the mirrors ineach section of alternate highand low reflecting power, the high reflecting power of these mirrorscorresponding approximately to that of the mirrors of the inner andouter concentric row of mirrors.

4. As an article of manufacture, a concave reflecting condenser havingconcentric graduated portions, of which the outer concentric portion isof higher reflecting power than the adjacent concentric portions.

5. As an article of manufacture, a concave reflecting condenser havingconcentric reflecting portions each formed of segmental mirrors, themirrors in the outermost and innermost concentric reflecting portionshaving uniform high reflecting power, and the mirrors of eachintermediate concentrlc reflecting portion being alternately of high andlow reflecting power.

6. As an article of manufacture, a concave reflecting condenser having acentral opening and concentric outermost, innermost and intermediatereflecting portions, the reflecting power of the outermost and inner--most portions exceeding that of the intermediate portions.

7. As an artic cave reflecting condenser having a central opening andconcentric rows of mirrors, the reflecting power of the outermost andinnermost rows of mirrors being approximately equal and exceeding thatof the intermediate rows of mirrors.

ROBERT D. GRAY.

le of manufacture, a con-'

